Needle guide systems are known in connection with ultrasonic transducers for removal of samples from internal organs.
A first needle guide system is a rigid system mounted on the side of the transducer, and which ensures that the needle is inserted in the ultrasonic image plane and imaged on the display associated with the ultrasonic transducer. Such a system requires relatively much room and accordingly it can only be used in connection with open operations (laparotomy). Relatively short needles are used which may be rather thick.
The same principle may apply to an ultrasonic transducer where the needle is inserted together with the transducer through a trocar tube. In this manner, ultrasound guided biopsies can be performed through the trocar tube. The latter is referred to as laparoscopic ultrasound-guided biopsy. The advantage of such a procedure is that the operational wound is smaller than the wound resulting from the first system. However, like the first needle guide system, this system only allows removal of tissue samples in one direction, viz. in an outward direction from the insertion point. Such a procedure is not always sufficient, for instance in connection with removal of tissue samples from organs full of blood, such as a liver, where the shortest possible insertion of the needle into the tissue is desired.
Furthermore, a flexible needle guide system is known, which is used together with an endoscope with an ultrasonic transducer built thereon, cf. PENTAX ultrasound upper G. I. fibrescope type FG-320A. A needle placed in a spiral is inserted through the endoscope into a channel which ensures that once the needle has left the channel and been inserted into the tissue, it is moved into the image plane of the transducer and imaged on a display associated with the transducer. The endoscope is flexible and suited for insertion through the natural openings of the body, such as through the mouth and the gullet and down into the stomach. The flexibility of the endoscope renders it unsuited for removal of biopsies from internal organs in the abdominal cavity because the positioning and the retaining of the instrument in the desired position are only possible in tubular cavities, such as inside the gullet. A drawback of the latter transducer is that the measuring system must be very flexible in order to be suited for ultrasound-guided biopsies at a predetermined depth, because the needle must then be able to withstand a bending of a relatively small radius.